Pattern generation methods and apparatuses

ABSTRACT

A method may comprise emitting electromagnetic radiation onto a workpiece and storing data describing geometrical elements in a pattern. The electromagnetic radiation may be focused and/or reflected in a first direction, and a power level of the electromagnetic radiation may be modulated according to the stored data. A guiding rail may be moved in the first direction and a carriage may be moved in a second direction, each in one of a continuous and stepwise manner. The second direction may be substantially perpendicular to the first direction. A pattern may be exposed on the workpiece.

PRIORITY STATEMENT

This non-provisional U.S. application is a continuation-in-part under 35U.S.C. § 111(a) of PCT International Application No. PCT/SE2004/000233,which has an international filing date of Feb. 20, 2004, whichdesignated the United States of America, and which claims priority under35 U.S.C. § 119 of Swedish Patent Applicant No. 0300453-8, filed on Feb.20, 2003, the entire contents of both of which are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Example embodiments of the present invention relate to methods andapparatuses for exposing a workpiece and/or the formation of patternsthereon using, for example, laser lithography on substrates such asboards (e.g., printed circuit boards (PCBs) or flexible PCBs), artworks,masks for liquid crystal displays (LCD), plasma display panels (PDP),thin film transistor displays (TFT), etc.

2. Description of the Conventional Art

In conventional methods for manufacturing masks, a pattern may beexposed in a photo resist, for example, an opaque film (e.g., chromium)on a transparent substrate (e.g., quartz). In a conventional develop andetch process the resist in the exposed areas may be removed and theunprotected film may be dissolved by an etchant (e.g., chromiumetchant). As a result, a glass plate with an opaque pattern (e.g.,opaque chromium) may be used as an optical contact and/or projectionmask for production of, for example, a conductor pattern on glass platesof an LCD, PDP, TFT and/or any other suitable display. The glass platesmay be coated with a photo resist or emulsion and exposed through theoptical mask (e.g., optical chromium mask). In conventional methods ofmanufacturing a mask, patterns of increasing complexity may be writtenon the mask and the glass plates may be reproduced.

Active matrix displays may require writing of elements of, for example,600 nm, which may require a geometrical error on the order of about 0.03parts per million (pap) or, for example, about 40 nm in the smallerdirection of a 1900×1200 mm plate.

Conventional exposure tools for creating larger displays (e.g., “flatpanel” displays), for example, as discussed in U.S. Pat. No. 5,495,279,the entire contents of which are incorporated herein by reference, mayhave a stage moving in an x and/or y-direction under a fixed or a movingwriting head, and may be operated in an environment (e.g., a particlefree environment) where the floor space may be increasingly expensive.

SUMMARY OF THE INVENTION

One or more example embodiments of the present invention provide methodsfor exposing plates used in displays, for example, without creating amask. One or more example embodiments of the present invention alsoprovide exposure tools with reduced volume, which may control and/orstabilize a temperature of a writing chamber. One or more exampleembodiments of the present invention provide exposure tools, whichprovide higher quality and/or more accurate critical dimension controlof a printed pattern.

One or more example embodiments of the present invention provide anapparatus, which may be more economical during manufacture, transportand/or operation.

In a method according to an example embodiment of the present invention,electromagnetic radiation may be emitted onto a workpiece, and datadescribing geometrical elements in a pattern may be stored. Theelectromagnetic radiation may be deflected and focused in a firstdirection, and a power of the electromagnetic radiation may be modulatedaccording to the stored data. A guiding rail may be moved in the firstdirection and a carriage may be moved in a second direction, the firstand second directions each may be one of a continuous and stepwise, andthe second direction may be perpendicular or substantially perpendicularto the first direction. The pattern may be exposed on the workpiece.

An apparatus for exposing a workpiece according to another exampleembodiment of the present invention may include an optical system whichmay deflect and/or focus electromagnetic radiation in a first directionrelative to the workpiece, and may modulate a power of theelectromagnetic radiation in accordance with at least a portion of thedata describing geometrical elements in a pattern. A guiding rail mayinclude a carriage and may be capable of moving in at least a firstdirection in one of a continuous or stepwise manner. The carriage may becapable of moving in a second direction in one of a continuous orstepwise manner, and the first and second directions may beperpendicular or substantially perpendicular to each other. Theworkpiece may be kept at a fixed position during exposure.

An optical system according to another example embodiment of the presentinvention may include a modulator and a deflector. The modulator mayvary at least one of an illumination time and an intensity ofelectromagnetic radiation emitted from a laser source. The deflector maydeflect and/or relay the electromagnetic radiation toward a workpiece,for example, after the modulator varies at least one of the illuminationtime and the intensity of electromagnetic radiation. The deflectedelectromagnetic radiation may be usable to expose the workpiece.

An optical system according to another example embodiment of the presentinvention may include a beam splitter, at least one spatial lightmodulator, a first lens and a second lens. The beam splitter maypartition a laser beam into a plurality of laser beams. The at least onespatial light modulator may include a plurality of pixels, may receivethe plurality of laser beams and relay the plurality of laser beamstoward a workpiece. The first lens may project the relayed plurality oflaser beams onto a spatial filter, which may be adapted to block out atleast a portion of the projected plurality of laser beams, and thesecond lens may form an image on the workpiece.

In example embodiments of the present invention, the data may be storedin at least one database and the deflecting and focusing may beperformed by an optical head mounted on the carriage.

In example embodiments of the present invention, the modulating may beperformed by at least one spatial light modulator positioned on thecarriage. The at least one spatial light modulator may have a pluralityof object pixels adapted to receive the electromagnetic radiation andrelay the electromagnetic radiation toward the workpiece.

In example embodiments of the present invention, the workpiece may bepositioned in a horizontal, substantially horizontal, vertical, orsubstantially vertical direction during exposure.

In example embodiments of the present invention, the laser may be fixedto or separate from the guiding rail, and/or the carriage may include amodulator for modulating the optical power.

In example embodiments of the present invention, a modulator formodulating the optical power may be arranged at a fixed distance from alaser source emitting the electromagnetic radiation.

In example embodiments of the present invention, the optical system mayfurther include a deflector and/or a modulator. The deflector maydeflect and/or focus the electromagnetic radiation in the firstdirection relative to the workpiece. The modulator may modulate thepower of the electromagnetic radiation in accordance with the at least aportion of the data.

In example embodiments of the present invention, the modulator mayinclude at least one spatial light modulator including a plurality ofpixels, adapted to receive the electromagnetic radiation and relay theelectromagnetic radiation toward the workpiece.

In example embodiments of the present invention, the electromagneticradiation may be a laser beam and/or the optical system may furtherinclude a beam splitter, at least one spatial light modulator, a firstand a second lens. The beam splitter may partition the laser beam into aplurality of laser beams. The at least one spatial light modulator mayinclude a plurality of pixels, which may receive the plurality of laserbeams and relay the plurality of laser beams toward the workpiece. Thefirst lens may project the relayed plurality of laser beams onto aspatial filter, and the spatial may be adapted to block out at least aportion of the projected plurality of laser beams. The second lens mayform an image on a workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an apparatus according to an example embodiment ofthe present invention;

FIG. 2 illustrates an optical system according to an example embodimentof the present invention;

FIG. 3 illustrates an optical system according to another exampleembodiment of the present invention; and

FIG. 4 illustrates example waist and wave fronts of a Gaussian laserbeam according to example embodiments of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE PRESENT INVENTION

The following detailed description is made with reference to thedrawings, which illustrate example embodiments of the present invention.However, these example embodiments of the present invention aredescribed to illustrate the present invention, not to limit its scope.Those of ordinary skill in the art will recognize a variety ofequivalent variations on the description that follows.

Example embodiments of the present invention will be described withreference to an analogue spatial light modulator (SLM). However, it willbe understood that any other suitable SLM may be used; for example,digital SLMs such as a digital micro-mirror device. Additionally, SLMsmay include reflective and/or transmissive deflectable modulatingelements (e.g., pixels, pixel elements, mirror elements, reflectiveelements, micro-mirrors, etc., any or all of which may be comprised of,for example, micronium or any suitable metal alloy).

Example embodiments of the present invention will be described withregard to an excimer laser source. However, it will be understood thatany suitable radiation source (e.g., electromagnetic and/or pulsedelectromagnetic radiation) such as a Nd—YAG laser, ion laser, Tisapphire laser, free electron laser, any other pulsed fundamentalfrequency lasers, flash lamps, laser plasma sources, synchrotron lightsources, etc., may be used.

As shown in FIG. 1, an apparatus according to an example embodiment ofthe present invention may include a support structure 13 capable ofsupporting a workpiece 10. A writing head including an optical system 2for generating object pixels on the workpiece 10 and a final lens 3 maybe placed on a carriage 14. The carriage 14 may slide along a guidingrail 16, for example, in an x-direction 15. Parts, which may move withthe carriage 14, are shown hatched in FIG. 1. The guiding rail 16 mayalso move in a y-direction 9. In example embodiments of the presentinvention, the guiding rail 16 may move in a stepwise, or substantiallystepwise, or a continuous or substantially continuous, fashion and/orthe carriage 14 may move in a stepwise, or substantially stepwise, or acontinuous, or substantially continuous, fashion. The stepwise movementmay be, for example, a slower and the continuous motion may be, forexample, a faster movement.

Alternatively, in example embodiments of the present invention, theworkpiece 10 may be in a fixed, or substantially fixed, position whilepatterned, and the support structure 13 may be arranged on a dampingstructure (e.g., vibration damping structure) 18. The damping structure18 may include, for example, a higher density material and may besupported by an air cushion, which may also damp vibrations.

As shown in FIG. 1, an end leg of the guiding rail 16 is omitted forvisibility. The optical system 2 may generate a scan line, which mayinclude, for example, several hundred pixels. The pixels may be written,for example, in the y-direction 9 for each x position along the guidingrail 16. A plurality of scan lines may form a strip, and a plurality ofpattern strips may form a pattern. The pattern strips may or may not atleast partly overlap each other, depending on the writing method.

As illustrated in FIG. 2, the optical system 2 may include a modulator90 and a deflector 95. The modulator 90 may change the period ofillumination time and/or intensity of the electromagnetic radiation fromthe source 17, and may be, for example, a conventional modulator (e.g.acousto-optical modulator) or any other suitable modulator with similar,or substantially similar, functionality. The deflector 95 may deflectthe beam of radiation for creating the pattern strips, and may be aconventional deflector (e.g., an acousto-optical deflector) or any othersuitable deflector. The pixel clock connectable to the modulator may usea frequency of, for example, about 50 MHz; although any suitablefrequency may be used. A length of the scan line, (e.g., a width of astrip) may be, for example, about 200 μm. In example embodiments of thepresent invention, the scan line may include, for example, about 800pixels.

In another example embodiment of the present invention, the opticalsystem 2 may include the deflector 95 and may not include the modulator90. In this example embodiment, the modulator 90 may be arranged at afixed position from the laser source 17.

FIG. 3 illustrates an optical system, according to another exampleembodiment of the present invention. As illustrated in FIG. 3, theoptical system 2 may include an SLM 80, a beam splitter 81, a tube lens(e.g., a compounded tube lens) 82 and a spatial filter 85. As shown inFIG. 3, the SLM 80 may be operated, for example, in an analog mode, andthe tube lens 82 and the spatial filter 85 together may form a Fourierfilter. The tube lens 82 may project the diffracted pattern onto thespatial filter 85 and the lens (e.g., a compounded final lens) 3, mayform an image (e.g., an aerial image) on the workpiece 10.

The spatial filter 85 may be, for example, an aperture in a plate, whichmay be sized and/or positioned in order to suppress (e.g., block out)orders of diffraction (e.g., each diffraction order) greater than orequal to the first diffraction order. In one example, the aperture maybe located at a focal distance from the tube lens 82, and reflectedradiation may be collected by the tube lens 82 in a focal plane, whichmay also be a pupil plane of the final lens 3. In this example, theaperture may suppress (e.g., block out) the radiation from the first andhigher diffraction orders from addressed pixels (e.g., micro-mirrors,etc.) in the SLM 80, while the radiation from the non-addressed pixelsmay pass the aperture. This may provide an intensity modulated image(e.g., aerial image) on the workpiece 10. In another example, for animage area with increasing darkness (e.g., optimum darkness) thediffraction pattern may contain radiation in the first and higherdiffraction orders and may not contain radiation in the zeroth order.

In example embodiments of the present invention, the SLM 80 may build apattern using, for example, stamps stitched together and which may atleast partially overlap each other. A stamp may be an image of the SLM80 at an image plane where the workpiece 10 may be arranged, and thepattern may be created using at least one exposure. If a plurality ofexposures are used, stamps in a first exposure may be translated in atleast one direction relative to stamps in a second exposure.

In an example embodiment of the present invention, the optical system 2may include a plurality of SLM chips, which may be arranged next to eachother, and which may have the same or different number of pixels and/orpixel geometrics.

In example embodiments of the present invention, radiation may begenerated by a laser source 17, which may be positioned (e.g., fixedand/or mounted) on the guiding rail 16 or separated from the guidingrail 16. The radiation may be expanded, collimated, homogenized andemitted (e.g., launched) by an optical system 19 in a directionparallel, or substantially parallel, to the guiding rail 16, such thatit may impinge pick-up optics 21 on the carriage 14, with unchanged, orsubstantially unchanged, lateral position, angle and/or cross sectionduring movement along the guiding rail 16.

The laser source 17 may be a continuous, or substantially continuous,laser source and the optical system 2 may include a modulator and adeflector, for example, the modulator 90 and the deflector 95 of FIG. 2.If the laser source 17 is, for example, a pulsed excimer laser, theoptical system 2 may include an SLM, for example, the SLM of FIG. 3, andthe wavelength of the laser may be, for example, in the ultra-violet(UV), deep ultraviolet (DUV) or extreme ultra-violet (EUV) range. If thewavelength is in the EUV range, at least a portion (e.g., the majority)of the majority optics may be reflective rather than refractive.

Alignment of the guiding rail 16 with the workpiece may be performed,for example, using interferometers in a conventional manner known by theskilled artisan and therefore need not be further explained. Theworkpiece 10 may be translated in any suitable manner using, forexample, piezo-electrical actuators arranged on at least one end of thesupport structure 13.

FIG. 4 illustrates an example expansion of a beam before the beam may belaunched toward the moving guiding rail 16 and carriage 14. A laser beam20 having higher (e.g., suitable or good) quality may have a Gaussianwaist 68 in which the diameter of the beam 20 may be reduced (e.g., aminimum). At the waist 68 the wave front 67 of the beam may be flat;however, wave fronts 60 of the beam away from the waist 68 may becurved. In example embodiments of the present invention, the wave fronts60 may exist, for example, at any distance from the waist 68. The sourcedistance may affect the true position of focus after the focusing lens3. When the carriage 14 with the optical system 2 and the final lens 3mounted thereon slides along the guiding rail 16, the curvature of thewave front 67 may be changed, such that a focus (e.g., a true focus) maybe below the workpiece 10 and/or away from the laser source 17 and/orabove the workpiece 10 at distances closer to the laser source 17. Whenthe laser source 17 is not fixed to the guiding rail 16, the distancefrom the laser source 17 to the guiding rail 16 and the carriage 14 maybe taken into account. The curvature variation may be determined, forexample, by the wavelength and/or the diameter at the waist 68, and withan unexpanded laser beam the useful range 69 may be less than themechanical stroke of the carriage 14 and/or the guiding rail 16. With awider waist 68 produced after the beam expander 19 the wave front may beflatter, for example, at each wave front, the focus shift may be smallerand/or the useful range may be larger than the mechanical stroke of theguiding rail 16 and the carriage 14 together.

In the example embodiment of the present invention as illustrated inFIG. 1, for example, the workpiece 10 may be arranged in parallel, orsubstantially parallel, with an x-y plane. This x-y plane may be ahorizontal, or substantially horizontal, plane or a vertical, orsubstantially vertical, plane. If the x-y plane is a vertical, orsubstantially vertical, plane, the workpiece 10 may be a standingsubstrate. Example embodiments of the present invention may occupy areduced amount of surface area in a clean room (e.g., footprint). Forexample, with a standing substrate 10, the substrate may be lesssensitive to contamination, for example, since an exposed areavulnerable to falling particles may be reduced (e.g., substantiallyreduced). In example embodiments of the present invention, the substratemay also be inclined at any angle between about 0° and about 90° fromthe horizontal plane.

Sag is a deformation of the workpiece due to a substrate's weight. Apattern of sag may depend on the type of structures supporting thesubstrate, the number of support structures, the size and/or geometry ofthe substrate.

In example embodiments of the present invention, a stepping motor, alinear motor, air bearings, and/or any other suitable device may movethe guiding rail 16. For example, a bearing may be positioned under eachleg of the guiding rail 16.

In another example embodiment of the present invention (e.g., as shownin FIG. 4), the legs of the guiding rail 16 may be coupled to each otherand may form a frame structure. This frame structure may include anupper part on which the carriage 14 may move in the x-direction and alower part including bearings along the y-direction. The lower part maybe below the damping structure 18, for example, a hollow part of theframe structure may move over the workpiece having the upper part abovethe workpiece 10 and the lower part below the workpiece 10.

In example embodiments of the present invention, mechanical and/orelectronic servos on the guiding rail 16 or the support structure 13 maybe used for positioning (e.g., fine positioning).

In an example embodiment of the present invention, there may be aplurality of motors (e.g., two linear motors) operating on the guidingrail 16 for performing movement in the y-direction, and the linearmotors may perform positioning by rotating the guiding rail 16. Therotation may be limited by the bearing(s) attached to the guiding rail16 for movement in the y-direction.

At an end support of the support structure 13 actuators (e.g.,piezoelectric actuators) may be attached displacing the supportstructure 13 in the y-direction. The actuators may be driven by voltages(e.g., analog voltages) from a control system including, for example,interferometers and/or a feedback circuits sensing the position of thesupport structure 13 relative to that of the guiding rail 16 byinterferometry. The actuators may correct the limited resolution in thestepping motor and/or non-straight travel over the guiding rail 16. Eachactuator may have a movement range of, for example, about 100 μm.

The guiding rail 16 may also be adjusted to compensate for theresolution (e.g., limited resolution) of the motor (e.g., stepping orlinear motor). In a similar manner actuators may be attached to theguiding rail 16 and using interferometry, for example, the position ofthe support structure 13 relative to the guiding rail 16 may bemonitored (e.g., constantly).

In example embodiments of the present invention (e.g., as illustrated inFIG. 1) the carriage 14 may slide on bearings 22 along the guiding rail16. The carriage 14 may be driven by a motor (e.g., linear electricmotor) 23 and may not contact (e.g., physically contact) the guidingrail 16 other than through electric cables and/or air supply tubes. Thecarriage 14 may be moved using the contact-less motor 23 and/or inertia.

Calibration may be used to compensate for errors concerning thestraightness of the guiding rail 16. For example, after the machine isassembled a test plate may be written and the writing errors measured.The writing errors may be stored in a calibration file and fed to thecontrol system as compensation during subsequent writing.

In example embodiments of the present invention, the deflector 95 in theoptical system 2, which may be mounted above (e.g., immediately above)the lens 3 may be used to form scan lines. Pixels may be, for example,about 300 nm×300 nm and each scan line may be, for example, about 200 μmwide. In example embodiments of the present invention, the lens 3 maybe, for example, a flat-field corrected lens with a numerical apertureless than or equal to about 0.14, and a focal length of, for example,about 4 mm.

Positioning (e.g., fine positioning) in the x-direction may be based onthe timing of a start-of-scan pulse when the lens 3 is at a first (e.g.,correct) position. In the y-direction the mechanical servos describedabove may be supplemented by a data delay, which may move data along theacousto-optical scan. Example embodiments of the present invention mayprovide an inertia-free feed forward control system having increasedbandwidth of the position control to, for example, greater than, orequal to, about 100 Hz.

Angle deviations from stroke to stroke of the carriage 14 may be, forexample, less than about 10 micro radians, and there may not be anyfocus shift along the stroke. In example embodiments of the presentinvention, the carriage 14 may slide on bearings (e.g., air bearings)with a higher stiffness, and a position of the carriage 14 relative tothe guiding rail 16 may be defined and/or independent of external airpressure and/or temperature. An imperfect guiding rail 16 may result ina writing error along the scan line. However, this error may be measuredduring calibration, stored as a correction curve and fed to the positionfeed back system for compensation during, for example, subsequentwriting. Focus may be kept constant, or substantially constant, bymanipulating the laser beam via collimating and/or beam shaping optics19.

When using an optical system according to example embodiments of thepresent invention (e.g., as shown in FIGS. 2 and/or 3), a laser beam maybe split into a plurality of beams using a beam splitter (not shown).

Example embodiments of the present invention provide a writer capable ofwriting for patterns of, for example, about 1900 mm×1200 mm, about 2100mm×1500 mm or any other suitable size. The damping structure may beformed by granite block and may be larger, or substantially larger, insize than the pattern to be written.

In example embodiments of the present invention a database describinggeometrical elements in a pattern may be included in or separate from anapparatus for patterning a workpiece.

While example embodiments of the present invention have been describedby reference to the drawings, it will be understood that these and otherexample embodiments are intended in an illustrative rather thanlimiting. It will also be understood that modifications and/orcombinations will readily occur to the skilled artisan, whichmodifications and/or combinations will be within the spirit of thepresent invention and the scope of the following claims.

1. A method comprising: emitting electromagnetic radiation toward aworkpiece; storing data describing geometrical elements in a pattern;moving a guiding rail in the first direction in a continuous or stepwisemanner, and moving a carriage in a second direction in a continuous orstepwise manner, the second direction being substantially perpendicularto the first direction; and exposing the pattern on the workpiece;wherein the workpiece is kept at a fixed position during exposure. 2.-3.(canceled)
 4. The method of claim 1, wherein the workpiece is positionedin a vertical, substantially vertical, horizontal, or substantiallyhorizontal direction during exposure.
 5. The method of claim 1, whereinthe laser is fixed to the guiding rail.
 6. The method of claim 1,wherein the laser is separate from the guiding rail. 7.-8. (canceled) 9.An apparatus for exposing a workpiece, comprising: an optical systemproviding electromagnetic radiation in a first direction relative to aworkpiece; a guiding rail capable of moving in at least a firstdirection in one of a continuous or stepwise manner and including acarriage capable of moving in a second direction in one of a continuousor stepwise manner, the first and second directions being perpendicularor substantially perpendicular to each other; wherein the workpiece iskept at a fixed position during exposure.
 10. The apparatus of claim 9,wherein the electromagnetic radiation includes at least one laser beam.11. The apparatus of claim 9, wherein the workpiece is positioned in avertical, substantially vertical, horizontal or substantially horizontaldirection during exposure.
 12. The apparatus of claim 9, wherein thelaser is fixed to the guiding rail.
 13. The apparatus of claim 9,wherein the at least one laser is separated from the guiding rail. 14.The apparatus of claim 9, wherein the modulator is arranged at a fixeddistance from a source of the electromagnetic radiation. 15.-22.(canceled)